A permanent magnet synchronous motor includes a stator and a rotor. Magnetic steel grooves are arranged in the rotor, and permanent magnets are provided in the magnet steel slots. During the operation, the rotor is driven to run by a permanent magnet torque and a reluctance torque. An output torque of the permanent magnet synchronous motor is illustrated in the following formula:T=mp(Lq−Ld)idiq+mpΨPMiq 
where, the first item in the formula, mp(Lq−Ld)idiq is the reluctance torque; the second item in the formula, mpΨPMiq is the permanent magnet torque; ΨPM is a maximum value of stator-rotor coupling magnetic flux generated by the permanent magnets; m is the phase number of a conductor of the stator conductor; p is the number of pole-pairs of the motor; Ld and Lq are inductances along d-axis and q-axis respectively; and id and iq are components of an armature current in the directions of d-axis and q-axis.
In practice, multiple stator teeth are provided on the stator of the permanent magnet synchronous motor, and multiple magnetic tunnels are formed in the stator. The magnetic flux lines are formed between the stator and the rotor (especially between the stator teeth and the magnetic tunnels). Thus, a torque for driving the rotor turning is formed by the full utilization of the reluctance torque. In an existing permanent magnet synchronous motor, there is an arbitrary corresponding relationship between the stator tooth and the magnetic tunnel, which determines the distribution of magnetic flux lines and the value of permanent magnet torque. In this way, an instable output torque and a large noise and vibration may be produced in the permanent magnet synchronous motor with the existing structure.